As the critical dimension of metal oxide semiconductor field effect transistor (MOSFET) devices continues to shrink, the short channel effect becomes more problematic. Fin field effect transistor (FinFET) devices have good control capability of gates to effectively suppress the short channel effect. FinFET devices can also reduce random dopant fluctuation to improve the stability of the devices. Thus, FinFET devices are widely used in the design of small-sized semiconductor elements.
A reduced feature size of a semiconductor device leads to problems of punch through effect. In order to prevent punch through a channel stop implant is placed at the bottom portion of the fin. However, for an NMOS device, dopants of the channel stop implant are typically boron or difluoride ions; after annealing for activation of the implanted dopants, due to random dopant fluctuation, the implanted dopants of the channel stop implant will easily diffuse into the channel, thereby greatly degrading the performance of the device, such as lowering the carrier mobility.
In order to suppress the diffusion of dopants into the channel, an amorphous layer is generally formed in the fin. However, the present inventor discovered that the current process includes firstly forming a shallow trench isolation (STI), then performing a channel stop implant, so that the amorphous layer will disappear after a high-temperature annealing process. Thus, the implanted dopants will diffuse into the channel after the channel stop ion implantation.
Therefore, there is a need for an improved fin-type FET device and method for manufacturing the same to overcome the above drawbacks